Signaling of global motion vector in picture header

ABSTRACT

A decoder includes circuitry configured to receive a bitstream, extract a header, determine, using the header, a global motion model, and decode a current block of a current frame using the global motion model. Related apparatus, systems, techniques and articles are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending application Ser. No.17/672,420 filed on Feb. 15, 2022, and entitled “SIGNALING OF GLOBALMOTION VECTOR IN PICTURE HEADER,” which is a continuation of U.S.Nonprovisional application Ser. No. 17/006,521, filed on Aug. 28, 2020and entitled “SIGNALING OF GLOBAL MOTION VECTOR IN PICTURE HEADER,”which is a continuation of International Application No. PCT/US20/29944,filed on Apr. 24, 2020 and entitled “SIGNALING OF GLOBAL MOTION VECTORIN PICTURE HEADER,” which claims the benefit of priority of U.S.Provisional Patent Application Ser. No. 62/838,509, filed on Apr. 25,2019, and titled “SIGNALING OF GLOBAL MOTION VECTOR IN PICTURE HEADER,”each of which is hereby incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of videocompression. In particular, the present invention is directed tosignaling of global motion vector in picture header.

BACKGROUND

A video codec can include an electronic circuit or software thatcompresses or decompresses digital video. It can convert uncompressedvideo to a compressed format or vice versa. In the context of videocompression, a device that compresses video (and/or performs somefunction thereof) can typically be called an encoder, and a device thatdecompresses video (and/or performs some function thereof) can be calleda decoder.

SUMMARY OF THE DISCLOSURE

In an aspect, a decoder includes circuitry configured to receive abitstream, extract a header, determine, using the header, a globalmotion model, and decode a current block of a current frame using theglobal motion model.

In another aspect, a method includes receiving, by a decoder, abitstream. The method includes extracting a header from the bitstream.The method includes determining, using the header, a global motionmodel. The method includes decoding a current block of a current frameusing the global motion model.

These and other aspects and features of non-limiting embodiments of thepresent invention will become apparent to those skilled in the art uponreview of the following description of specific non-limiting embodimentsof the invention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a diagram illustrating motion vectors of an example frame withglobal and local motion;

FIG. 2 illustrates three example motion models that can be utilized forglobal motion including their index value (0, 1, or 2);

FIG. 3 is a process flow diagram according to some exampleimplementations of the current subject matter;

FIG. 4 is a system block diagram of an example decoder according to someexample implementations of the current subject matter;

FIG. 5 is a process flow diagram according to some exampleimplementations of the current subject matter;

FIG. 6 is a system block diagram of an example encoder according to someexample implementations of the current subject matter; and

FIG. 7 is a block diagram of a computing system that can be used toimplement any one or more of the methodologies disclosed herein and anyone or more portions thereof.

The drawings are not necessarily to scale and may be illustrated byphantom lines, diagrammatic representations and fragmentary views. Incertain instances, details that are not necessary for an understandingof the embodiments or that render other details difficult to perceivemay have been omitted.

DETAILED DESCRIPTION

“Global motion” in video refers to motion and/or a motion model commonto all pixels of a region, where a region may be a picture, a frame, orany portion of a picture or frame such as a block, CTU, or other subsetof contiguous pixels. Global motion may be caused by camera motion, suchas without limitation, camera panning and zooming creates motion in aframe that can typically affect the entire frame. Motion present inportions of a video may be referred to as local motion. Local motion maybe caused by moving objects in a scene; for instance and withoutlimitation, local motion may be caused by an object moving from left toright in the scene. Videos may contain a combination of local and globalmotion. Some implementations of current subject matter may provide forefficient approaches to communicate global motion to a decoder and useof global motion vectors in improving compression efficiency.

FIG. 1 is a diagram illustrating an exemplary embodiment of motionvectors of an example frame 100 with global and local motion. Frame 100may include a number of blocks of pixels illustrated as squares, andtheir associated motion vectors illustrated as arrows. Squares (e.g.,blocks of pixels) with arrows pointing up and to the left indicateblocks with motion that may be considered to be global motion andsquares with arrows pointing in other directions (indicated by 104)indicate blocks with local motion. In the illustrated example of FIG. 1, many of the blocks have same global motion. Signaling global motion ina header, such as a picture parameter set (PPS) or sequence parameterset (SPS) and using signal global motion may reduce motion vectorinformation needed by blocks and can result in improved prediction.Although for illustrative purposes examples described below refer todetermination and/or application of global or local motion vectors at ablock level, global motion vectors may be determined and/or applied forany region of a frame and/or picture, including regions made up ofmultiple blocks, regions bounded by any geometric form such as withoutlimitation regions defined by geometric and/or exponential coding inwhich one or more lines and/or curves bounding the shape may be angledand/or curved, and/or an entirety of a frame and/or picture. Althoughsignaling is described herein as being performed at a frame level and/orin a header and/or parameter set of a frame, signaling may alternativelyor additionally be performed at a sub-picture level, where a sub-picturemay include any region of a frame and/or picture as described above.

As an example, and continuing to refer to FIG. 1 , simple translationalmotion may be described using a motion vector (MV) with two componentsMV_(x), MV_(y) that describes displacement of blocks and/or pixels in acurrent frame. More complex motion such as rotation, zooming, andwarping may be described using affine motion vectors, where an “affinemotion vector,” as used in this disclosure, is a vector describing auniform displacement of a set of pixels or points represented in a videopicture and/or picture, such as a set of pixels illustrating an objectmoving across a view in a video without changing apparent shape duringmotion. Some approaches to video encoding and/or decoding may use4-parameter or 6-parameter affine models for motion compensation ininter picture coding.

For example, and still referring to FIG. 1 , a six-parameter affinemotion model may describe affine motion as:

x′=ax+by +c

y′=dx+ey+f

A four-parameter affine motion can be described as:

x′=ax+by +c

y′=−bx+ay+f

where (x,y) and (x′,y′) are pixel locations in current and referencepictures, respectively; a, b, c, d, e, and f may represent parameters ofthe affine motion model.

With continued reference to FIG. 1 , parameters used describe affinemotion are signaled to the decoder to apply affine motion compensationat the decoder. In some approaches, motion parameters may be signaledexplicitly or by signaling translational control point motion vectors(CPMVs) and then deriving affine motion parameters from thetranslational motion vectors. Two control point motion vectors (CPMVs)may be utilized to derive affine motion parameters for a four-parameteraffine motion model and three control point translational motion vectors(CPMVs) may be utilized to obtain parameters for a six-parameter motionmodel. Signaling affine motion parameters using control point motionvectors may allow use of efficient motion vector coding methods tosignal affine motion parameters.

In some implementations, and further referring to FIG. 1 , global motionsignaling may be included in a header, such as the PPS or SPS. Globalmotion may vary from picture to picture. Motion vectors signaled inpicture headers may describe motion relative to previously decodedframes. In some implementations, global motion may be translational oraffine. A motion model (e.g., number of parameters, whether the model isaffine, translational, or other) used may also be signaled in a pictureheader.

Referring now to FIG. 2 , three non-limiting exemplary embodiments ofmotion models 200 that may be utilized for global motion including theirindex value (0, 1, or 2) are illustrated.

Still referring to FIG. 2 , a PPS may be used to signal parameters thatchange between pictures of a sequence. Parameters that remain the samefor a sequence of pictures may be signaled in a sequence parameter setto reduce the size of PPS and reduce video bitrate. An example pictureparameter set (PPS) is shown in table 1:

pic_parameter_set_rbsp( ) { Descriptor  pps_pic_parameter_set_id ue(v) pps_seq_parameter_set_id u(4)  mixed_nalu_types_in_pic_flag u(1) pic_width_in_luma_samples ue(v)  pic_height_in_luma_samples ue(v) pps_conformance_window_flag u(1)  if( pps_conformance_window_flag ) {  pps_conf_win_left_offset ue(v)   pps_conf_win_right_offset ue(v)  pps_conf_win_top_offset ue(v)   pps_conf_win_bottom_offset ue(v)  } scaling_window_explicit_signalling_flag u(1)  if(scaling_window_explicit_signalling_flag ) {   scaling_win_left_offsetue(v)   scaling_win_right_offset ue(v)   scaling_win_top_offset ue(v)  scaling_win_bottom_offset ue(v)  }  output_flag_present_flag u(1) subpic_id_mapping_in_pps_flag u(1)  if( subpic_id_mapping_in_pps_flag ){   pps_num_subpics_minus1 ue(v)   pps_subpic_id_len_minus1 ue(v)   for(i = 0; i <= pps_num_subpic_minus1; i++ )    pps_subpic_id[ i ] u(v)  } no_pic_partition_flag u(1)  if( !no_pic_partition_flag ) {  pps_log2_ctu_size_minus5 u(2)   num_exp_tile_columns_minus1 ue(v)  num_exp_tile_rows_minus1 ue(v)   for( i = 0; i <=num_exp_tile_columns_minus1; i++ )    tile_column_width_minus1[ i ]ue(v)   for( i = 0; i <= num_exp_tile_rows_minus1; i++ )   tile_row_height_minus1[ i ] ue(v)   if( NumTilesInPic > 1 )   rect_slice_flag u(1)   if( rect_slice_flag )   single_slice_per_subpic_flag u(1)   if( rect_slice_flag &&!single_slice_per_subpic_flag ) {    num_slices_in_pic_minus1 ue(v)   if( num_slices_in_pic_minus1 > 0 )     tile_idx_delta_present_flagu(1)    for( i = 0; i < num_slices_in_pic_minus1; i++ ) {     if(NumTileColumns > 1 )      slice_width_in_tiles_minus1 [ i ] ue(v)    if( NumTileRows > 1 && ( tile_idx_delta_present_flag | |      SliceTopLeftTileIdx[ i ] % Num TileColumns = = 0 ) )     slice_height_in_tiles_minus1[ i ] ue(v)     if(slice_width_in_tiles_minus1[ i ] = = 0 &&      slice_height_in_tiles_minus1[ i ] = = 0 &&       RowHeight[SliceTopLeftTileIdx[ i ] / NumTileColumns ] > 1 ) {     num_exp_slices_in_tile[ i ] ue(v)      for(j = 0; j <num_exp_slices_in_tile[ i ]; j++ )      exp_slice_height_in_ctus_minus1[ i ][ j ] ue(v)      i +=NumSlicesInTile[ i ] − 1     }     if( tile_idx_delta present_flag && i< num_slices_in_pic_minus1 )      tile_idx_delta[ i ] se(v)    }   }  loop_filter_across_tiles_enabled_flag u(1)  loop_filter_across_slices_enabled_flag u(1)  } cabac_init_present_flag u(1)  for( i = 0; i < 2; i++ )  num_ref_idx_default_active_minus1[ i ] ue(v)  rpl1_idx_present_flagu(1)  init_qp_minus26 se(v)  cu_qp_delta_enabled_flag u(1) pps_chroma_tool_offsets_present_flag u(1)  if(pps_chroma_tool_offsets_present_flag ) {   pps_cb_qp_offset se(v)  pps_cr_qp_offset se(v)   pps_joint_cbcr_qp_offset_present_flag u(1)  if( pps_joint_cbcr_qp_offset_present_flag )   pps_joint_cbcr_qp_offset_value se(v)  pps_slice_chroma_qp_offsets_present_flag u(1)  pps_cu_chroma_qp_offset_list_enabled_flag u(1)  }  if(pps_cu_chroma_qp_offset_list_enabled_flag ) {  chroma_qp_offset_list_len_minus1 ue(v)   for( i = 0; i <=chroma_qp_offset_list_len_minus1; i++ ) {    cb_qp_offset_list[ i ]se(v)    cr_qp_offset_list[ i ] se(v)    if(pps_joint_cbcr_qp_offset_present_flag )     joint_cbcr_qp_offset_list[ i] se(v)    }  }  pps_weighted_pred_flag u(1)  pps_weighted_bipred_flagu(1)  deblocking_filter_control_present_flag u(1)  if(deblocking_filter_control_present_flag ) {  deblocking_filter_override_enabled_flag u(1)  pps_deblocking_filter_disabled_flag u(1)   if(!pps_deblocking_filter_disabled_flag ) {    pps_beta_offset_div2 se(v)   pps_tc_offset_div2 se(v)    pps_cb_beta_offset_div2 se(v)   pps_cb_tc_offset_div2 se(v)    pps_cr_beta_offset_div2 se(v)   pps_cr_tc_offset_div2 se(v)   }  }  rpl_info_in_ph_flag u(1)  if(deblocking_filter_override_enabled_flag )   dbf_info_in_ph_flag u(1) sao_info_in_ph_flag u(1)  alf_info_in_ph_flag u(1)  if( (pps_weighted_pred_flag | | pps_weighted_bipred_flag ) &&rpl_info_in_ph_flag )   wp_info_in_ph_flag u(1) qp_delta_info_in_ph_flag u(1)  pps_ref_wraparound_enabled_flag u(1) if( pps_ref_wraparound_enabled_flag )   pps_ref_wraparound_offset ue(v) picture_header_extension_present_flag u(1) slice_header_extension_present_flag u(1)  pps_extension_flag u(1)  if(pps_extension_flag )   while( more_rbsp_data( ) )   pps_extension_data_flag u(1)  rbsp_trailing_bits( ) }

Continuing to refer to FIG. 2 , additional fields may be added to a PPSto signal global motion. In case of global motion, presence of globalmotion parameters in a sequence of pictures may be signaled in a SPS andPPS may reference the SPS by SPS ID. An SPS in some approaches todecoding may be modified to add a field to signal presence of globalmotion parameters in SPS. For example a one-bit field may be added to anSPS. If global_motion_present bit is 1, global motion related parametersmay be expected in a PPS. If global_motion_present bit is 0, no globalmotion parameter related fields may be present in a PPS. For example, aPPS as illustrated in table 1 may be extended to include aglobal_motion_present field, for example, as shown in table 2:

sequence_parameter_set_rbsp( ) { Descriptor sps_sequence_parameter_set_id ue(v) . . . global_motion_present u(1) rbsp_trailing_bits( ) }

Similarly, and still referring to FIG. 2 , a PPS may include apps_global_motion_parameters field for a frame, for example as shown intable 3:

pic_parameter_set_rbsp( ) { Descriptor  pps_pic_parameter_set_id ue(v) pps_seq_parameter_set_id ue(v) . . . pps_global_motion_parameters ( ) rbsp_trailing_bits( ) }

In more detail, and with continued reference to FIG. 2 , a PPS mayinclude fields to characterize global motion parameters using controlpoint motion vectors, for example as shown in table 4:

pps_global_motion_parameters ( ) { Descriptor motion_model_used u(2)mv0_x se(v) mv1_y se(v) if(motion_model_used == 1){  mv1_x se(v)  mv1_yse(v) } if(motion_model_used == 2){  mv2_x se(v)  mv2_y se(v) } }

As a further non-limiting example, Table 5 below may represent anexemplary SPS:

seq_parameter_set_rbsp( ) { Descriptor  sps_seq_parameter_set_id u(4) sps_video_parameter_set id u(4)  sps_max_sublayers_minus1 u(3) sps_reserved_zero_4bits u(4)  sps_ptl_dpb_hrd_params_present_flag u(1) if( sps_ptl_dpb_hrd_params_present_flag )   profile_tier_level( 1,sps_max_sublayers_minus1 )  gdr_enabled_flag u(1)  chroma_format_idcu(2)  if( chroma format_idc = = 3 )   separate_colour_plane_flag u(1) res_change_in_clvs_allowed_flag u(1)  pic_width_max_in_luma_samplesue(v)  pic_height_max_in_luma_samples ue(v)  sps_conformance_window_flagu(1)  if( sps_conformance_window_flag ) {   sps_conf_win_left_offsetue(v)   sps_conf_win_right_offset ue(v)   sps_conf_win_top_offset ue(v)  sps_conf_win_bottom_offset ue(v)  }  sps_log2_ctu_size_minus5 u(2) subpic_info_present_flag u(1)  if( subpic_info_present_flag ) {  sps_num_subpics_minus1 ue(v)   sps_independent_subpics_flag u(1)  for( i = 0; sps_num_subpics_minus1 > 0 && i <= sps_num_subpics_minus1;i++ ) {    if( i > 0 && pic_width_max_in_luma_samples > CtbSizeY )    subpic_ctu_top_left_x[ i ] u(v)    if( i > 0 &&pic_height_max_in_luma_samples > CtbSizeY ) {     subpic_ctu_top_left_y[i ] u(v)    if( i < sps_num_subpics_minus1 &&     pic_width_max_in_luma_samples > CtbSizeY )     subpic_width_minus1[i ] u(v)    if( i < sps_num_subpics_minus1 &&     pic_height_max_in_luma_samples > CtbSizeY )    subpic_height_minus1[ i ] u(v)    if( !sps_independent_subpics_flag){     subpic_treated_as_pic_flag[ i ] u(1)    loop_filter_across_subpic_enabled_flag[ i ] u(1)    }   }  sps_subpic_id_len_minus1 ue(v)  subpic_id_mapping_explicitly_signalled_flag u(1)   if(subpic_id_mapping_explicitly_signalled_flag ) {   subpic_id_mapping_in_sps_flag u(1)    if(subpic_id_mapping_in_sps_flag )     for( i = 0; i <=sps_num_subpics_minus1; i++ )      sps_subpic_id[ i ] u(v)   }  } bit_depth_minus8 ue(v)  sps_entropy_coding_sync_enabled_flag u(1)  if(sps_entropy_coding_sync_enabled_flag )  sps_wpp_entry_point_offsets_present_flag u(1)  sps_weighted_pred_flagu(1)  sps_weighted_bipred_flag u(1)  log2_max_pic_order_cnt_lsb_minus4u(4)  sps_poc_msb_flag u(1)  if( sps_poc_msb_flag )   poc_msb_len_minus1ue(v)  num_extra_ph_bits_bytes u(2)  extra_ph_bits_struct(num_extra_ph_bits_bytes )  num_extra_sh_bits_bytes u(2) extra_sh_bits_struct( num_extra_sh_bits_bytes )  if(sps_max_sublayers_minus1 > 0 )   sps_sublayer_dpb_params_flag u(1)  if(sps_ptl_dpb_hrd_params_present_flag )   dpb_parameters(sps_max_sublayers_minus1, sps_sublayer_dpb_params_flag ) long_term_ref_pics_flag u(1)  inter_layer_ref_pics_present_flag u(1) sps_idr_rpl_present_flag u(1)  rpl1_same_as_rpl0_flag u(1)  for( i = 0;i < rpl1_same_as_rpl0_flag ? 1 : 2; i++ ) {   num_ref_pic_lists_in_sps[i ] ue(v)   for(j = 0; j < num_ref_pic_lists_in_sps[ i ]; j++)   ref_pic_list_struct( i, j )  }  if( ChromaArrayType != 0 )  qtbtt_dual_tree_intra_flag u(1) log2_min_luma_coding_block_size_minus2 ue(v) partition_constraints_override_enabled_flag u(1) sps_log2_diff_min_qt_min_cb_intra_slice_luma ue(v) sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v)  if(sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {  sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v)  sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v)  } sps_log2_diff_min_qt_min_cb_inter_slice ue(v) sps_max_mtt_hierarchy_depth_inter_slice ue(v)  if(sps_max_mtt_hierarchy_depth_inter_slice != 0 ) {  sps_log2_diff_max_bt_min_qt_inter_slice ue(v)  sps_log2_diff_max_tt_min_qt_inter_slice ue(v)  }  if(qtbtt_dual_tree_intra_flag ) {  sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)  sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v)   if(sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {   sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v)   sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v)   }  } sps_max_luma_transform_size_64_flag u(1)  if( ChromaArrayType != 0 ) {  sps_joint_cbcr_enabled_flag u(1)   same_qp_table_for_chroma u(1)  numQpTables = same_qp_table_for_chroma ? 1 : (sps_joint_cbcr_enabled_flag ? 3 : 2 )   for( i = 0; i < numQpTables; i++) {    qp_table_start_minus26[ i ] se(v)   num_points_in_qp_table_minus1[ i ] ue(v)    for(j = 0; j <=num_points_in_qp_table_minus1[ i ]; j++ ) {     delta_qp_in_val_minus1[i ][ j ] ue(v)     delta_qp_diff_val[ i ][ j ] ue(v)    }   }  } sps_sao_enabled_flag u(1)  sps_alf_enabled_flag u(1)  if(sps_alf_enabled_flag && ChromaArrayType != 0 )   sps_ccalf_enabled_flagu(1)  sps_transform_skip_enabled_flag u(1)  if(sps_transform_skip_enabled_flag ) {  log2_transform_skip_max_size_minus2 ue(v)   sps_bdpcm_enabled_flagu(1)  }  sps_ref_wraparound_enabled_flag u(1) sps_temporal_mvp_enabled_flag u(1)  if( sps_temporal_mvp_enabled_flag )  sps_sbtmvp_enabled_flag u(1)  sps_amvr_enabled_flag u(1) sps_bdof_enabled_flag u(1)  if( sps_bdof_enabled_flag )  sps_bdof_pic_present_flag u(1)  sps_smvd_enabled_flag u(1) sps_dmvr_enabled_flag u(1)  if( sps_dmvr_enabled_flag)  sps_dmvr_pic_present_flag u(1)  sps_mmvd_enabled_flag u(1) sps_isp_enabled_flag u(1)  sps_mrl_enabled_flag u(1) sps_mip_enabled_flag u(1)  if( ChromaArrayType != 0 )  sps_cclm_enabled_flag u(1)  if( chroma_format_idc = = 1 ) {  sps_chroma_horizontal_collocated_flag u(1)  sps_chroma_vertical_collocated_flag u(1)  }  sps_mts_enabled_flag u(1) if( sps_mts_enabled_flag ) {   sps_explicit_mts_intra_enabled_flag u(1)  sps_explicit_mts_inter_enabled_flag u(1)  } six_minus_max_num_merge_cand ue(v)  sps_sbt_enabled_flag u(1) sps_affine_enabled_flag u(1)  if( sps_affine_enabled_flag ) {  five_minus_max_num_subblock_merge_cand ue(v)   sps_affine_type_flagu(1)   if( sps_amvr_enabled_flag )    sps_affine_amvr_enabled_flag u(1)  sps_affine_prof_enabled_flag u(1)   if( sps_affine_prof_enabled_flag )   sps_prof_pic_present_flag u(1)  }  sps_palette_enabled_flag u(1)  if(ChromaArrayType == 3 && !sps_max luma transform size_64 flag )  sps_act_enabled_flag u(1)  if( sps_transform_skip_enabled_flag | |sps_palette_enabled_flag )   min_qp_prime_ts_minus4 ue(v) sps_bcw_enabled_flag u(1)  sps_ibc_enabled_flag u(1)  if(sps_ibc_enabled_flag )   six_minus_max_num_ibc_merge_cand ue(v) sps_ciip_enabled_flag u(1)  if( sps_mmvd_enabled_flag )  sps_fpel_mmvd_enabled_flag u(1)  if( MaxNumMergeCand >= 2 ) {  sps_gpm_enabled_flag u(1)   if( sps_gpm_enabled_flag &&MaxNumMergeCand >= 3 )    max_num_merge_cand_minus_max_num_gpm_candue(v)  }  sps_lmcs_enabled_flag u(1)  sps_lfnst_enabled_flag u(1) sps_ladf_enabled_flag u(1)  if( sps_ladf_enabled_flag ) {  sps_num_ladf_intervals_minus2 u(2)  sps_ladf_lowest_interval_qp_offset se(v)   for( i = 0; i <sps_num_ladf intervals_minus2 + 1; i++ ) {    sps_ladf_qp_offset[ i ]se(v)    sps_ladf_delta_threshold_minus1[ i ] ue(v)   }  } log2_parallel_merge_level_minus2 ue(v) sps_explicit_scaling_list_enabled_flag u(1)  sps_dep_quant_enabled_flagu(1)  if( !sps_dep_quant_enabled_flag )  sps_sign_data_hiding_enabled_flag u(1) sps_virtual_boundaries_enabled_flag u(1)  if(sps_virtual_boundaries_enabled_flag ) {  sps_virtual_boundaries_present_flag u(1)   if(sps_virtual_boundaries_present_flag ) {   sps_num_ver_virtual_boundaries u(2)    for( i = 0; i <sps_num_ver_virtual_boundaries; i++ )     sps_virtual_boundaries_pos_x[i ] u(13)    sps_num_hor_virtual_boundaries u(2)    for( i = 0; i <sps_num hor_virtual_boundaries; i++ )     sps_virtual_boundaries_pos_y[i ] u(13)   }  }  if( sps_ptl_dpb_hrd_params_present_flag ) {  sps_general_hrd_params_present_flag u(1)   if(sps_general_hrd_params_present_flag ) {    general_hrd_parameters( )   if( sps_max_sublayers_minus1 > 0 )    sps_sublayer_cpb_params_present_flag u(1)    firstSubLayer =sps_sublayer_cpb_params_present_flag ? 0 :      sps_max_sublayers_minus1   ols_hrd_parameters( firstSubLayer, sps_max_sublayers_minus1 )   }  } field_seq_flag u(1)  vui_parameters_present_flag u(1)  if(vui_parameters_present_flag )   vui_parameters( ) /* Specified in ITU-TH.SEI | ISO/IEC 23002-7 */  sps_extension_flag u(1)  if(sps_extension_flag )   while( more_rbsp_data( ) )   sps_extension_data_flag u(1)  rbsp_trailing_bits( ) }

An SPS table as above may be expanded as described above to incorporatea global motion present indicator as shown in Table 6:

sequence_parameter_set_rbsp( ) { Descriptor sps_sequence_parameter_set_id ue(v) . . . global_motion_present u(1) rbsp_trailing_bits( ) }

Additional fields may be incorporated in an SPS to reflect furtherindicators as described in this disclosure.

In an embodiment, and still referring to FIG. 2 , ansps_affine_enabled_flag may specify whether affine model based motioncompensation may be used for inter prediction. Ifsps_affine_enabled_flag is equal to 0, the syntax may be constrainedsuch that no affine model based motion compensation is used in the codelater video sequence (CLVS), and inter_affine_flag andcu_affine_type_flag may not be present in coding unit syntax of theCLVS. Otherwise (sps_affine_enabled_flag is equal to 1), affine modelbased motion compensation can be used in the CLVS.

Continuing to refer to FIG. 2 , sps_affine_type_flag may specify whether6-parameter affine model based motion compensation may be used for interprediction. If sps_affine_type_flag is equal to 0, syntax may beconstrained such that no 6-parameter affine model based motioncompensation is used in the CLVS, and cu_affine_type_flag may notpresent in coding unit syntax in the CLVS. Otherwise(sps_affine_type_flag equal to 1), 6-parameter affine model based motioncompensation may be used in CLVS. When not present, the value ofsps_affine_type_flag may be inferred to be equal to 0.

Still referring to FIG. 2 , translational CPMVs may be signaled in aPPS. Control points may be predefined. For example, control point MV 0may be relative to a top left corner of a picture, MV 1 may be relativeto a top right corner, and MV 3 may be relative to a bottom left cornerof a picture. Table 4 illustrates an example approach for signaling CPMVdata depending on the motion model used.

In an exemplary embodiment, and still referring to FIG. 2 , an arrayamvr_precision_idx, which may be signaled in coding unit, coding tree,or the like, may specify a resolution AmvrShift of a motion vectordifference, which may be defined as a non-limiting example as shown inTable 7 as shown below. Array indices x0, y0 may specify the location(x0, y0) of a top-left luma sample of a considered coding block relativeto a top-left luma sample of the picture; whenamvr_precision_idx[x0][y0] is not present, it may be inferred to beequal to 0. Where an inter_affine_flag[x0][y0] is equal to 0, variablesMvdL0[x0][y0][0], MvdL0[x0][y0][1], MvdL1[x0][y0][0], MvdL1[x0][y0][1]representing modsion vector difference values corresponding to conseredblock, may be modified by shifting such values by AmvrShift, forinstance using MvdL0[x0][y0][0]=MvdL0[x0][y0][0]<<AmvrShift;MvdL0[x0][y0][1]=MvdL0[x0][y0][1]<<AmvrShift;MvdL1[x0][y0][0]=MvdL1[x0][y0][0]<<AmvrShift; andMvdL1[x0][y0][1]=MvdL1[x0][y0][1]<<AmvrShift. Whereinter_affine_flag[x0][y0] is equal to 1, variablesMvdCpL0[x0][y0][0][0], MvdCpL0[x0][y0][0][1], MvdCpL0[x0][y0][1][0],MvdCpL0[x0][y0][1][1], MvdCpL0[x0][y0][2][0] and MvdCpL0[x0][y0][2][1]may be modified via shifting, for instance as follows:MvdCpL0[x0][y0][0][0]=MvdCpL0[x0][y0][0][0]<<AmvrShift; MvdCpL1[x0][y0][0][1]=MvdCpL1[x0][y0][0][1]<<AmvrShift;MvdCpL0[x0][y0][1][0]=MvdCpL0[x0][y0][1][0]<<AmvrShift; MvdCpL1[x0][y0][1][1]=MvdCpL1[x0][y0][1][1]<<AmvrShift;MvdCpL0[x0][y0][2][0]=MvdCpL0[x0][y0][2][0]<<AmvrShift; andMvdCpL1[x0][y0] [2][1]=MvdCpL1[x0][y0][2][1]<<AmvrShift

AmvrShift inter_affine_flag = =0 & & inter_affine_flag CuPredMode[chType ][ x0 ] CuPredMode[ chType ][ x0 ] amvr_flag amvr_precision_id == 1 [ y0 ] = = MODE_IBC ) [ y0 ] != MODE_IBC 0 — 2 (1/4 luma sample) — 2(1/4 luma sample) 1 0 0 (1/16 luma sample) 4 (1 luma sample) 3 (1/2 lumasample) 1 1 4 (1 luma sample) 6 (4 luma samples) 4 (1 luma sample) 1 2 —— 6 (4 luma samples)

With continued reference to FIG. 2 , global motion may be relative to apreviously coded frame. When only one set of global motion parametersare present, motion may be relative to a frame that is presentedimmediately before a current frame.

FIG. 3 is a process flow diagram illustrating an example process 300 ofsignaling global motion model for decoding that can improve compressionefficiency.

At step 305, and still referring to FIG. 3 , a bitstream is received bya decoder. A current block may be contained within a bitstream thatdecoder receives. Bitstream may include, for example, data found in astream of bits that is an input to a decoder when using datacompression. Bitstream may include information necessary to decode avideo. Receiving may include extracting and/or parsing a block andassociated signaling information from bit stream. In someimplementations, a current block may include a coding tree unit (CTU), acoding unit (CU), or a prediction unit (PU). At step 310, a header maybe extracted from bitstream. At step 315, a global motion model may bedetermined using the header; determination of global motion model may beperformed as above, including by determination as signaled in a PPSand/or SPS. At step 320, a current block of a current frame may bedecoded using a determined global motion model.

FIG. 4 is a system block diagram illustrating an example decoder 400capable of decoding a bitstream 428 with signaling global motion modelthat can improve compression efficiency. Decoder 400 may include anentropy decoder processor 404, an inverse quantization and inversetransformation processor 408, a deblocking filter 412, a frame buffer416, motion compensation processor 420 and intra prediction processor424.

In operation, and still referring to FIG. 4 , a bit stream 428 may bereceived by decoder 400 and input to entropy decoder processor 404,which entropy decodes portions of the bit stream into quantizedcoefficients. Quantized coefficients may be provided to inversequantization and inverse transformation processor 408, which may performinverse quantization and inverse transformation to create a residualsignal, which may be added to an output of motion compensation processor420 or intra prediction processor 424 according to a processing mode. Anoutput of motion compensation processor 420 and intra predictionprocessor 424 may include a block prediction based on a previouslydecoded block. A sum of prediction and residual may be processed by adeblocking filter 630 and stored in a frame buffer 640.

FIG. 5 is a process flow diagram illustrating an example process 500 ofencoding a video with signaling global motion that can improvecompression efficiency according to some aspects of the current subjectmatter. At step 505, a video frame may undergo initial blocksegmentation, for example, using a tree-structured macro blockpartitioning scheme that may include partitioning a picture frame intoCTUs and CUs. At step 510, global motion for a current block may bedetermined. Determining global motion may include determining a globalmotion model and associated parameters. At step 515, global motionmodel, associated parameters, and block may be encoded and included in abitstream. Encoding may include utilizing inter prediction and intraprediction modes, for example.

FIG. 6 is a system block diagram illustrating an example video encoder600 capable of signaling global motion that can improve compressionefficiency. Example video encoder 600 may receive an input video 604,which may be initially segmented or dividing according to a processingscheme, such as a tree-structured macro block partitioning scheme (e.g.,quad-tree plus binary tree). An example of a tree-structured macro blockpartitioning scheme may include partitioning a picture frame into largeblock elements called coding tree units (CTU). In some implementations,each CTU may be further partitioned one or more times into a number ofsub-blocks called coding units (CU). A final result of this portioningmay include a group of sub-blocks that may be called predictive units(PU). Transform units (TU) may also be utilized.

Still referring to FIG. 6 , example video encoder 600 may include anintra prediction processor 608, a motion estimation/compensationprocessor 612 (also referred to as an inter prediction processor)capable of supporting global motion signaling and processing, atransform/quantization processor 616, an inverse quantization/inversetransform processor 620, an in-loop filter 624, a decoded picture buffer628, and/or an entropy coding processor 632. Bit stream parameters maybe input to entropy coding processor 632 for inclusion in output bitstream 636.

In operation, and further referring to FIG. 6 , for each block of aframe of input video 604, whether to process the block via intra pictureprediction or using motion estimation/compensation may be determined.Block may be provided to intra prediction processor 608 or motionestimation/compensation processor 612. If block is to be processed viaintra prediction, intra prediction processor 608 may perform processingto output predictor. If block is to be processed via motionestimation/compensation, motion estimation/compensation processor 612may perform processing including global motion signaling, if applicable.

Still referring to FIG. 6 , a residual may be formed by subtractingpredictor from input video. Residual may be received bytransform/quantization processor 616, which may perform transformationprocessing (e.g., discrete cosine transform (DCT)) to producecoefficients, which may be quantized. Quantized coefficients and anyassociated signaling information may be provided to entropy codingprocessor 632 for entropy encoding and inclusion in output bit stream636. Entropy encoding processor 632 may support encoding of signalinginformation related to encoding current block. In addition, quantizedcoefficients may be provided to inverse quantization/inversetransformation processor 620, which mat reproduce pixels, which mat becombined with predictor and processed by in loop filter 624, an outputof which may be stored in decoded picture buffer 628 for use by motionestimation/compensation processor 612 that is capable of global motionsignaling and processing.

Although a few variations have been described in detail above, othermodifications or additions are possible. For example, in someimplementations, current blocks can include any symmetric blocks (8×8,16×16, 32×32, 64×64, 128×128, and the like) as well as any asymmetricblock (8×4, 16×8, and the like).

In some implementations, a quadtree plus binary decision tree (QTBT) maybe implemented. In QTBT, at the Coding Tree Unit level, partitionparameters of QTBT are dynamically derived to adapt to localcharacteristics without transmitting any overhead. Subsequently, at aCoding Unit level, a joint-classifier decision tree structure mayeliminate unnecessary iterations and control risk of false prediction.In some implementations, LTR frame block update mode may be available asan additional option available at every leaf node of QTBT.

In some implementations, additional syntax elements may be signaled atdifferent hierarchy levels of a bitstream. For example, a flag may beenabled for an entire sequence by including an enable flag coded in aSequence Parameter Set (SPS). Further, a CTU flag may be coded at thecoding tree unit (CTU) level.

It is to be noted that any one or more of the aspects and embodimentsdescribed herein may be conveniently implemented using digitalelectronic circuitry, integrated circuitry, specially designedapplication specific integrated circuits (ASICs), field programmablegate arrays (FPGAs) computer hardware, firmware, software, and/orcombinations thereof, as realized and/or implemented in one or moremachines (e.g., one or more computing devices that are utilized as auser computing device for an electronic document, one or more serverdevices, such as a document server, etc.) programmed according to theteachings of the present specification, as will be apparent to those ofordinary skill in the computer art. These various aspects or featuresmay include implementation in one or more computer programs and/orsoftware that are executable and/or interpretable on a programmablesystem including at least one programmable processor, which may bespecial or general purpose, coupled to receive data and instructionsfrom, and to transmit data and instructions to, a storage system, atleast one input device, and at least one output device. Appropriatesoftware coding may readily be prepared by skilled programmers based onthe teachings of the present disclosure, as will be apparent to those ofordinary skill in the software art. Aspects and implementationsdiscussed above employing software and/or software modules may alsoinclude appropriate hardware for assisting in the implementation of themachine executable instructions of the software and/or software module.

Such software may be a computer program product that employs amachine-readable storage medium. A machine-readable storage medium maybe any medium that is capable of storing and/or encoding a sequence ofinstructions for execution by a machine (e.g., a computing device) andthat causes the machine to perform any one of the methodologies and/orembodiments described herein. Examples of a machine-readable storagemedium include, but are not limited to, a magnetic disk, an optical disc(e.g., CD, CD-R, DVD, DVD-R, etc.), a magneto-optical disk, a read-onlymemory “ROM” device, a random access memory “RAM” device, a magneticcard, an optical card, a solid-state memory device, an EPROM, an EEPROM,Programmable Logic Devices (PLDs), and/or any combinations thereof. Amachine-readable medium, as used herein, is intended to include a singlemedium as well as a collection of physically separate media, such as,for example, a collection of compact discs or one or more hard diskdrives in combination with a computer memory. As used herein, amachine-readable storage medium does not include transitory forms ofsignal transmission.

Such software may also include information (e.g., data) carried as adata signal on a data carrier, such as a carrier wave. For example,machine-executable information may be included as a data-carrying signalembodied in a data carrier in which the signal encodes a sequence ofinstruction, or portion thereof, for execution by a machine (e.g., acomputing device) and any related information (e.g., data structures anddata) that causes the machine to perform any one of the methodologiesand/or embodiments described herein.

Examples of a computing device include, but are not limited to, anelectronic book reading device, a computer workstation, a terminalcomputer, a server computer, a handheld device (e.g., a tablet computer,a smartphone, etc.), a web appliance, a network router, a networkswitch, a network bridge, any machine capable of executing a sequence ofinstructions that specify an action to be taken by that machine, and anycombinations thereof. In one example, a computing device may includeand/or be included in a kiosk.

FIG. 7 shows a diagrammatic representation of one embodiment of acomputing device in the exemplary form of a computer system 700 withinwhich a set of instructions for causing a control system to perform anyone or more of the aspects and/or methodologies of the presentdisclosure may be executed. It is also contemplated that multiplecomputing devices may be utilized to implement a specially configuredset of instructions for causing one or more of the devices to performany one or more of the aspects and/or methodologies of the presentdisclosure. Computer system 700 includes a processor 704 and a memory708 that communicate with each other, and with other components, via abus 712. Bus 712 may include any of several types of bus structuresincluding, but not limited to, a memory bus, a memory controller, aperipheral bus, a local bus, and any combinations thereof, using any ofa variety of bus architectures.

Memory 708 may include various components (e.g., machine-readable media)including, but not limited to, a random-access memory component, a readonly component, and any combinations thereof. In one example, a basicinput/output system 716 (BIOS), including basic routines that help totransfer information between elements within computer system 700, suchas during start-up, may be stored in memory 708. Memory 708 may alsoinclude (e.g., stored on one or more machine-readable media)instructions (e.g., software) 720 embodying any one or more of theaspects and/or methodologies of the present disclosure. In anotherexample, memory 708 may further include any number of program modulesincluding, but not limited to, an operating system, one or moreapplication programs, other program modules, program data, and anycombinations thereof.

Computer system 700 may also include a storage device 724. Examples of astorage device (e.g., storage device 724) include, but are not limitedto, a hard disk drive, a magnetic disk drive, an optical disc drive incombination with an optical medium, a solid-state memory device, and anycombinations thereof. Storage device 724 may be connected to bus 712 byan appropriate interface (not shown). Example interfaces include, butare not limited to, SCSI, advanced technology attachment (ATA), serialATA, universal serial bus (USB), IEEE 1394 (FIREWIRE), and anycombinations thereof. In one example, storage device 724 (or one or morecomponents thereof) may be removably interfaced with computer system 700(e.g., via an external port connector (not shown)). Particularly,storage device 724 and an associated machine-readable medium 728 mayprovide nonvolatile and/or volatile storage of machine-readableinstructions, data structures, program modules, and/or other data forcomputer system 700. In one example, software 720 may reside, completelyor partially, within machine-readable medium 728. In another example,software 720 may reside, completely or partially, within processor 704.

Computer system 700 may also include an input device 732. In oneexample, a user of computer system 700 may enter commands and/or otherinformation into computer system 700 via input device 732. Examples ofan input device 732 include, but are not limited to, an alpha-numericinput device (e.g., a keyboard), a pointing device, a joystick, agamepad, an audio input device (e.g., a microphone, a voice responsesystem, etc.), a cursor control device (e.g., a mouse), a touchpad, anoptical scanner, a video capture device (e.g., a still camera, a videocamera), a touchscreen, and any combinations thereof. Input device 732may be interfaced to bus 712 via any of a variety of interfaces (notshown) including, but not limited to, a serial interface, a parallelinterface, a game port, a USB interface, a FIREWIRE interface, a directinterface to bus 712, and any combinations thereof. Input device 732 mayinclude a touch screen interface that may be a part of or separate fromdisplay 736, discussed further below. Input device 732 may be utilizedas a user selection device for selecting one or more graphicalrepresentations in a graphical interface as described above.

A user may also input commands and/or other information to computersystem 700 via storage device 724 (e.g., a removable disk drive, a flashdrive, etc.) and/or network interface device 740. A network interfacedevice, such as network interface device 740, may be utilized forconnecting computer system 700 to one or more of a variety of networks,such as network 744, and one or more remote devices 748 connectedthereto. Examples of a network interface device include, but are notlimited to, a network interface card (e.g., a mobile network interfacecard, a LAN card), a modem, and any combination thereof. Examples of anetwork include, but are not limited to, a wide area network (e.g., theInternet, an enterprise network), a local area network (e.g., a networkassociated with an office, a building, a campus or other relativelysmall geographic space), a telephone network, a data network associatedwith a telephone/voice provider (e.g., a mobile communications providerdata and/or voice network), a direct connection between two computingdevices, and any combinations thereof. A network, such as network 744,may employ a wired and/or a wireless mode of communication. In general,any network topology may be used. Information (e.g., data, software 720,etc.) may be communicated to and/or from computer system 700 via networkinterface device 740.

Computer system 700 may further include a video display adapter 752 forcommunicating a displayable image to a display device, such as displaydevice 736. Examples of a display device include, but are not limitedto, a liquid crystal display (LCD), a cathode ray tube (CRT), a plasmadisplay, a light emitting diode (LED) display, and any combinationsthereof. Display adapter 752 and display device 736 may be utilized incombination with processor 704 to provide graphical representations ofaspects of the present disclosure. In addition to a display device,computer system 700 may include one or more other peripheral outputdevices including, but not limited to, an audio speaker, a printer, andany combinations thereof. Such peripheral output devices may beconnected to bus 712 via a peripheral interface 756. Examples of aperipheral interface include, but are not limited to, a serial port, aUSB connection, a FIREWIRE connection, a parallel connection, and anycombinations thereof.

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments, what has been described herein is merelyillustrative of the application of the principles of the presentinvention. Additionally, although particular methods herein may beillustrated and/or described as being performed in a specific order, theordering is highly variable within ordinary skill to achieve embodimentsas disclosed herein. Accordingly, this description is meant to be takenonly by way of example, and not to otherwise limit the scope of thisinvention.

In the descriptions above and in the claims, phrases such as “at leastone of” or “one or more of” may occur followed by a conjunctive list ofelements or features. The term “and/or” may also occur in a list of twoor more elements or features. Unless otherwise implicitly or explicitlycontradicted by the context in which it is used, such a phrase isintended to mean any of the listed elements or features individually orany of the recited elements or features in combination with any of theother recited elements or features. For example, the phrases “at leastone of A and B;” “one or more of A and B;” and “A and/or B” are eachintended to mean “A alone, B alone, or A and B together.” A similarinterpretation is also intended for lists including three or more items.For example, the phrases “at least one of A, B, and C;” “one or more ofA, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, Balone, C alone, A and B together, A and C together, B and C together, orA and B and C together.” In addition, use of the term “based on,” aboveand in the claims is intended to mean, “based at least in part on,” suchthat an unrecited feature or element is also permissible.

The subject matter described herein can be embodied in systems,apparatus, methods, and/or articles depending on the desiredconfiguration. The implementations set forth in the foregoingdescription do not represent all implementations consistent with thesubject matter described herein. Instead, they are merely some examplesconsistent with aspects related to the described subject matter.Although a few variations have been described in detail above, othermodifications or additions are possible. In particular, further featuresand/or variations can be provided in addition to those set forth herein.For example, the implementations described above can be directed tovarious combinations and sub-combinations of the disclosed featuresand/or combinations and sub-combinations of several further featuresdisclosed above. In addition, the logic flows depicted in theaccompanying figures and/or described herein do not necessarily requirethe particular order shown, or sequential order, to achieve desirableresults. Other implementations may be within the scope of the followingclaims.

What is claimed is:
 1. A computer-readable recording medium storing an encoded bitstream which is decodable by a decoder, the decoder comprising circuitry configured to: receive the encoded bitstream including a coded picture, the coded picture including a first region comprising a first contiguous plurality of coding blocks having global motion and a second region comprising a second contiguous plurality of coding blocks having local motion; for each block in the first region, determine a motion model, the motion model being global for all of the blocks in the first region and being one of translational motion, 4-parameter affine motion, or 6-parameter affine motion, the parameters of the motion model for each block in the first region being determined from at least one motion vector signaled in the bitstream; and decode each block in the first region using the parameters of the motion model to reconstruct the global motion in the first region; and for each block in the second region, decode each block using motion information determined individually for each block to reconstruct the local motion in the second region.
 2. The computer readable medium of claim 1, wherein the current block forms part of a quadtree plus binary decision tree.
 3. The computer readable recording medium of claim 1, wherein the current block is a coding tree unit.
 4. The computer readable recording medium of claim 1, wherein the current block is a coding unit.
 5. The computer readable recording medium of claim 1, wherein the motion model is an affine motion model and the motion vectors are control point motion vectors.
 6. The computer-readable recording medium of claim 5, wherein the affine motion model is 4-parameter affine motion model having two control point motion vectors.
 7. The computer-readable recording medium of claim 5, wherein the affine motion model is 6-parameter affine motion model having three control point motion vectors. 